V048K015T80 Datasheet, PDF (12/20 Pages) Vicor Corporation – VI Chip - VTM Voltage Transformation Module

Application Note (continued)
PRELIMINARY
Thermal Management
The high efficiency of the VTM results in low power
dissipation minimizing temperature rise, even at full output
current. The heat generated within the internal semiconductor
junctions is coupled through very low thermal resistances, RθJC
and RθJB (see Figure 25), to the PC board allowing flexible
thermal management.
CASE 1 Convection via optional Pin Fins to air (Pin Fins
available mounted to the V•I Chip or as a separate item.)
CASE 3 Combined direct convection to the air and conduction
to the PC board.
A combination of cooling techniques that utilize the power
planes and dissipation to the air will also reduce the total
thermal impedance. This is the most effective cooling
method.To estimate the total effect of the combination, treat
each cooling branch as one leg of a parallel resistor network.
In an environment with forced convection over the surface of a
PCB with 0.4" of headroom, a VTM with Pin Fins offers a
simple thermal management option. The total Junction to
Ambient thermal resistance of a surface mounted
V048L015T80 is 5 ºC/W in 300 LFM airflow, (see Figure 26).
At full rated current (80A) the VTM dissipates approximately
11 W. Power dissipation curves in Figure 6 show typical
dissipation at different output currents.
CASE 2 Conduction to the PC board
Figure 25—Thermal resistance
The low thermal resistance, Junction to BGA, allows the use of
the PC board as a means of removing heat from the VTM.
Convection from the PC board to ambient, or conduction to a
cold plate, enable flexible thermal management options. In this
case, the VTM can be used without the Pin Fin option, allowing
a system designer to take full advantage of the VTM’s low profile.
With a VTM mounted on a 2.0 in² area of a multi-layer PC
board with appropriate power planes resulting in 8 oz of
effective copper weight, the Junction-to-ambient thermal
resistance, RθJA, is 6.5 ºC/W in 300 LFM of air. With a
maximum junction temperature of 125ºC and 11 W of
dissipation at full current of 80 A, the resulting temperature rise
of 72ºC allows the VTM to operate at full rated current up to a
53ºC ambient temperature. See thermal resistance table on page
1 for additional details on this thermal management option.
Adding low-profile heat sinks to the PC board can lower the
thermal resistance of the PC board surrounding the VTM. This
option is useful in environments that cannot accommodate the
height of the Pin Fin option.
Additional cooling may be added by coupling a cold plate to
the PC board with low thermal resistance stand offs.
VTM with optional 0.25'' Pin Fins
10
9
8
7
6
5
4
3
0
100
200
300
400
500
600
Airflow (LFM)
Figure 26—Junction-to-ambient thermal resistance of VTM
with 0.25" Pin Fins. (Pin Fins are available as an option for
the V•I Chip package.)
45 ^{Vicor Corporation Tel: [phone] vicorpower.com}
V•I Chip Voltage Transformation Module Rev. 1.6
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